On Thu, 2010-04-08 at 21:17 +0200, Peter Zijlstra wrote:> plain text document attachment (powerpc-gup_fast-rcu.patch)> The powerpc page table freeing relies on the fact that IRQs hold off> an RCU grace period, this is currently true for all existing RCU> implementations but is not an assumption Paul wants to support.> > Therefore, also take the RCU read lock along with disabling IRQs to> ensure the RCU grace period does at least cover these lookups.

There's a few other places that need a similar fix then. The hash pagecode for example. All the C cases should end up calling thefind_linux_pte() helper afaik, so we should be able to stick the lock inthere (and the hugetlbfs variant, find_linux_pte_or_hugepte()).

However, we also have cases of tight asm code walking the page tables,such as the tlb miss handler on embedded processors. I don't see how Icould do that there. IE. I only have a handful of registers to playwith, no stack, etc...

So we might have to support the interrupt assumption, at least in someform, with those guys...